1. Field of the Invention. This invention relates to a slack adjuster for a disc brake and, more specifically, to such a slack adjuster which utilizes an adjusting sleeve threadably coupled to the brake piston for rotation relative thereto to adjust the axial position of the piston.
2. Description of the Prior Art. One type of disc brake which is well known in the automotive field utilizes a rotating disc or rotor which is mounted for rotation with a wheel. The brake includes a caliper assembly which is mounted on the axle with an extended, outboard portion which overlies the outboard side of the disc and a piston which is aligned with the inboard side of the disc. Axial movement of the piston causes the disc to be entrapped therebetweeen to produce a frictional force thereon tending to prevent rotation of the disc and wheel.
Both the extended portion and the piston employ brake shoe and friction pad configurations with the friction pads being made of a material which is worn away during the life of the brake as the surface thereon is repeatedly brought into frictional contact with the disc. However, during normal actuation of the brake, it is desirable for the piston to be maintained at a predetermined running clearance from the disc so that application of the brake will be assured after the piston has traveled through the relatively small, predetermined running clearance. With repeated use and extensive wear of the friction pads, it would be possible for the piston to remain at the same position relative to the disc prior to actuation to cause the running clearance to be enlarged sufficiently to prevent quick, reliable brake operation. Such extensive piston movement during actuation could complicate the operation of the actuation means and lengthen the time required to initially apply the brakes. Accordingly, it is not uncommon to employ a slack adjusting means within such a brake which is intended to insure that the running clearance will be maintained within a maximum distance throughout the life of the friction pads to insure that the brake will quickly produce frictional contact with the disc whenever the brake is being actuated.
Although there have heretofore been provided a number of slack adjuster means for insuring that the desired running clearance will be maintained throughout the operating life of such brakes, there remains a need for any slack adjuster which is reliable, effective and relatively simple to maintain. Two patent applications, U.S. Ser. No. 484,025, now U.S. Pat. No. 4,478,316 entitled "Slack Adjuster For A Disc Brake", filed by Donald J. Davidson on Apr. 11, 1983 and U.S. Ser. No. 484,026 now U.S. Pat. No. 4,478,317 entitled "Slack Adjuster For A Disc Brake", filed by David D. Sheill on Apr. 11, 1983, disclose adjusters which satisfy these requirements but do not include a means for verifying that adjustments are being made during the operating life of the brake.